The purpose of this multi-center, double-blind, placebo-controlled study was to evaluate the efficacy and safety of the experimental drug Acetyl-L-Carnitine when compared to placebo in the treatment of patients betweeen 45 and 65 years of age with early onset Alzheimer's Disease. Primary outcome measures included changes in memory assessed by neuropsychological tests; secondary measures included assessment of change in clinical status and functional measures. Patients who successfully completed the 12-month double-blind phase of the study and demonstrated compliance were given the option of continuing treatment with Acetyl-L-Carnitine in an open-label extension phase.